The present invention relates to a self-propelled colonoscope, which does not cause pain to a patient during a colonoscopic examination of the colon.
Colonoscopic examination is currently carried out by inserting a colonoscope by hand, such that the examination may cause pain to a patient by excessively extending or bending the colon.
FIG. 7 is a drawing schematically showing an insertion path of a conventional colonoscope.
The tip of the insertion tube 100 of the colonoscope is inserted from the anus 101 into the colon 103 and advances from the sigmoid colon 105 to the ileum 113, by passing through the descending colon 107, a transverse colon 109 and an ascending colon 111. The tip of the insertion tube 100 may be inserted until it reaches the distal end of the colon (A) or it may be inserted into the ileum 113 for about 25 cm (B).
As shown in FIG. 7, since the sigmoid colon 105, positioned near the insertion point of the colonoscope, is sharply bent and has an S-shape, considerable operator skill is necessary to pass the insertion tube 100 through this portion. Further, the procedure causes increased pain to the patient.
Accordingly, in order to reduce the pain to the patient, in Patent Application Number Hei. 11-99600, the inventor of the present invention has proposed a colonoscope self-propelled along the colon. The colonoscope can be self-inserted into the colon by driving endless belts arranged on the outside of the flexible section of the insertion tube.
In such colonoscope, the endless belts are driven and contact the outside thereof with a wall of the colon to introduce the tip of the colonoscope into the colon by friction between the colon wall and the endless belts.
An object of the invention is therefore to provide a self-propelled colonoscope having improved bending ability of the insertion tube and self-propelling ability.
According to an aspect of the present invention, a colonoscope which can be self-inserted into a colon by driving an endless belt arranged on the outside of a flexible section of an insertion tube is provided, wherein a cross section of said endless belt is substantially circular, rack gear teeth having a circular cross section are formed on the outside of the endless belt, and a recess having a semi-circular cross section and pinion gear teeth which correspond to the shapes of the endless belt and the rack gear teeth are formed on the outside of a pulley for driving the endless belt.
The endless belt has a vertical circular cross section with respect to the longitudinal axis so as to have constant flexibility in all radial directions to the axis, thereby flexibly bending in all radial directions. Thus, when the insertion tube is inserted along the bending of the sigmoid colon, the endless belt can easily follow the movement of the insertion tube.
Since the rack gear teeth are formed on the outside of the endless belt, a large friction force develops between the outside of the endless belt and the wall of the colon such that the self-propelling ability of the colonoscope is improved. Moreover, since the rack gear teeth are formed on the outside surface of the endless belt, if the endless belt should twist during operation, a part of the endless belt will contact and rub against the wall of the colon. Further, the pinion gear teeth and the recess formed on the outside of the pulley drive the endless belt such that the pulley is engaged with the endless belt tightly to increase the driving force of the endless belt.
Generally, the diameter of the insertion tube of a colonoscope conventionally used is 11.3 to 14.2 mm. When the tip of the colonoscope advances into the colon, the inner ring length and the outer ring length of the inserted insertion tube differ due to the bending of the colon. In the present invention, the length of the endless belt is 102 to 104% of a length such endless belt would have if it were tensely held around the inside and the outside of the insertion tube in the longitudinal direction while the insertion tube is kept straight. Thus the length of the insertion tube has an allowance corresponding to the difference between the lengths of the inner ring and the outer ring of the inserted insertion tube. Accordingly, the endless belt can follow the bending of the insertion tube and enables the colonoscope to advance into the colon stably. At this time, the endless belt and the pulley are tightly engaged and can not be disengaged regardless of any allowance of the endless belt. Further, the outside surface of the endless belt and the outside surface of the pulley may be coated with high frictional material so that the rack gear teeth and the pinion gear teeth will be engaged tightly thereby preventing the endless belt from running idle.
In the present invention, the outside surface of the endless belt may be coated with high frictional material. Thus, the friction force between the endless belt and the wall of the colon will be increased thereby improving the self-propelling ability.